Question

2. The largest grand piano in the world is really grand. Builtin
London, it has a mass of 1.25x103kg. Suppose apianist
finishes playing this piano and pushes herself from thepiano so
that she rolls backwards with a speed of 1.4m/s.Meanwhile, the
piano rolls forward so that in 4.0sec it travels 24cm at constant
velocity. Assuming the stool that the pianist issitting on has a
negligible mass, what is the pianist's mass?